My husband usually leaves his computer on all the time and when he woke up this morning, it was off, so when we hit the power button, it looks like it is going to start up normally - the disk drive buttons flash, the keyboard buttons flash, the monitor clicks like it is going to turn on - then the computer just shuts off before anything comes up on the monitor.

I opened the case because it was FILTHY! :o I cleaned all the fans because they were covered with crud and tried again, but it's the same thing.

I can tell you he runs Windows XP Pro, but it's an older computer that was built by a friend of his. If you need more info on it and can tell me where to look, I will.

Unplug power cord, open the case up, remove the battery from mobo for 5 mins, short the 2 pins next to the battery socket with the tip of a ballpen or pencil for 10 secs if they exist, put battery back in, plug power cord in, power on, tap DEL or whatever key is on screen for SETUP/BIOS, load defaults, save & exit, tap F8 before windows loads, select "disable automatically...".

Jot down the error code if windows goes to a blue screen of death. It's like 0x000000?? and maybe a filename. Google these.

Okay - I took out the battery for 5 min., but there were no pins except under the battery, there were two prongs like sticking up. I replaced it and plugged back in the power cord and tried to start it. There's also a switch on the back of the computer, like an on/off switch, that has to be on before you can turn on the power button on the front, so I had to do that. The first two times, it would do the same as before; the fans would come on, the lights would blink, the screen would click to come on and then click right back off and then the whole thing shuts down. The third time, however, the screen clicked on and off, but the fans stayed running and the power light stayed on, so I hit the reset button and it came on. I went into the BIOS and selected the load fail safe defaults. There was another choice for load optimized defaults. I saved/exited and hit the F8 key, but there wasn't any choice for "disable automatically". I just chose Start Windows normally. It came on with no error screen.

No problem. Ok, you're getting the pc to start up (POST). You're going somewhere. Tap F8 again right before windows load, & select safe mode. Run a few cleanup tools like "the cleaner", ccleaner, etc. Open up device manager & see if everything is up & running. Even do a scan disk in My Computer, right-click OS drive, Tools, scan now.

As a last resort, insert the windows setup disk & do a repair install when asked.

I also highly recommend that you back up anything and everything that you do not want to loose. Obviously the computer is not running at it's prime, and even if it was it would be wise to make backups. A lot of people have no idea how much time, money and sanity backups can save them until they've lost something that they "cannot loose"... Course, you may not really care about anything on it, but if you do, you know what to do.

Secondly, clean it out every once in a while. Heat can do bad, bad things to computers, and dust can cause a lot of it. Clogs up heatsinks and other airways reducing airflow, slows down or stops fans which even further reduces airflow, and insulates causing any airflow to be far less effective for cooling. It can also cause shorts in some situations. Basically, dust kills computers. Keep it clean and it will most likely run better, longer.